Clopidogrel is an oral, anti-platelet agent that is primarily used as blood thinner in conditions like coronary artery disease, peripheral vascular disease, myocardial infarction and cerebrovascular disease. CYP2C19 is a genetic determinant of efficacy of anti-platelet agent. CYP2C19 has marked impact on metabolism of various drugs including clopidogrel. Mutations in CYP2C19 gene leads to formation of many genotypic variants, which decides the metabolizer strata of patients. Optimization of clopidogrel dosage is based on the allele variant identified and pharmacogenetics of CYP2C19 gene.